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        handlebars遍历标签
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        <time class="time" datetime="2020-01-18T14:50:37.000Z">
        2020-01-18
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      <p>采用与上一篇文章一样的方法，使用 <code>ember generate route handlebars-each</code> 命令创建了一个路由文件和一个对应的模板文件。<br>这一篇将为你介绍遍历标签，数组的遍历几乎在任何的常用的开发语言中都能看到，也是使用非常广泛的一个功能。下面我将为大家介绍<code>handlebars</code>的遍历标签，其使用方式与EL表达式几乎是一样的。我想你看一遍下来肯定也能明白了⋯⋯废话少说，下面直接上演示代码吧！！</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//  app/routes/handlebars.js</span></span><br><span class="line"><span class="keyword">import</span> Ember <span class="keyword">from</span> <span class="string">&#x27;ember&#x27;</span>;</span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 定义一个用于测试的对象数组</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> Ember.Route.extend(&#123;</span><br><span class="line">    <span class="comment">//  重写model回调函数，初始化测试数据</span></span><br><span class="line">    model: <span class="function"><span class="keyword">function</span>(<span class="params"></span>) </span>&#123;</span><br><span class="line">        <span class="keyword">return</span> [</span><br><span class="line">            Ember.Object.create(&#123; <span class="attr">name</span>: <span class="string">&#x27;chen&#x27;</span>, <span class="attr">age</span>: <span class="number">25</span>&#125;),</span><br><span class="line">            Ember.Object.create(&#123; <span class="attr">name</span>: <span class="string">&#x27;i2cao.xyz&#x27;</span>, <span class="attr">age</span>: <span class="number">0.2</span>&#125;),</span><br><span class="line">            Ember.Object.create(&#123; <span class="attr">name</span>: <span class="string">&#x27;ibeginner.sinaapp.com&#x27;</span>, <span class="attr">age</span>: <span class="number">1</span>&#125;),</span><br><span class="line">            Ember.Object.create(&#123; <span class="attr">name</span>: <span class="string">&#x27;ubuntuvim.xyz&#x27;</span>, <span class="attr">age</span>: <span class="number">3</span>&#125;)</span><br><span class="line">        ];</span><br><span class="line">    &#125;</span><br><span class="line">&#125;);</span><br></pre></td></tr></table></figure>

<p>如上述所示，在<code>route</code>类里构建了一个用于测试的对象数组，每个对象有2个属性（<code>name</code>，<code>age</code>）。<br>下面是显示数据的模板：</p>
<figure class="highlight html"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!-- // app/templates/handlebars.hbs --&gt;</span></span><br><span class="line"></span><br><span class="line">&#123;&#123;! 遍历在route里设置的对象数组 &#125;&#125;</span><br><span class="line"><span class="tag">&lt;<span class="name">ul</span>&gt;</span></span><br><span class="line">    &#123;&#123;#each model as |item|&#125;&#125;</span><br><span class="line">        <span class="tag">&lt;<span class="name">li</span>&gt;</span>Hello everyone, My name is &#123;&#123;item.name&#125;&#125; and &#123;&#123;item.age&#125;&#125; year old.<span class="tag">&lt;/<span class="name">li</span>&gt;</span></span><br><span class="line">    &#123;&#123;/each&#125;&#125;</span><br><span class="line"><span class="tag">&lt;/<span class="name">ul</span>&gt;</span></span><br></pre></td></tr></table></figure>
<p>有没有似曾相似的感觉呢！！跟EL表达式的<code>forEach</code>标签几乎是一样的。不出意外你应该可以看到如下的结果。</p>
<p><img src="/content/images/2016/03/21.png" alt="run result"></p>
<p><strong>提醒：记得此时运行的URL是刚刚新建的route。</strong><br>操作数组的时候注意使用官方建议的方法（如，新增使用<code>pushObject</code>而不是<code>push</code>），请看<a target="_blank" rel="noopener" href="http://blog.ddlisting.com/2016/03/17/ember-js-ru-men-zhi-nan-zhi-liu-mei-ju-enumerables/">前面的文章</a>。</p>
<h3 id="1，访问数组下标"><a href="#1，访问数组下标" class="headerlink" title="1，访问数组下标"></a>1，访问数组下标</h3><p>有些情况我们可能需要获取数组的下标，比如有些时候可能会下标作为数据的序号。请看下面的演示：</p>
<figure class="highlight html"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!-- // app/templates/handlebars.hbs --&gt;</span></span><br><span class="line"></span><br><span class="line">&#123;&#123;! 遍历在route里设置的对象数组 &#125;&#125;</span><br><span class="line"><span class="tag">&lt;<span class="name">ul</span></span></span><br><span class="line"><span class="tag">    &#123;&#123;#<span class="attr">each</span> <span class="attr">model</span> <span class="attr">as</span> |<span class="attr">item</span> <span class="attr">index</span>|&#125;&#125;</span></span><br><span class="line">        &lt;li&gt;&#123;&#123;index&#125;&#125; Hello everyone, My name is &#123;&#123;item.name&#125;&#125; and &#123;&#123;item.age&#125;&#125; year old.&lt;/li&gt;</span><br><span class="line">    &#123;&#123;/each&#125;&#125;</span><br><span class="line"><span class="tag">&lt;/<span class="name">ul</span>&gt;</span></span><br></pre></td></tr></table></figure>
<p>不过这个下标是从0开始的，且你还不能想jstl中的<code>forEach</code>标签可以这样写<code>{{index+1}}</code>，<code>handlebars</code>不允许这么写！如果你想改成从1开始那么可以使用helper实现。正如网友<code>@吧台丶香槟</code>所说的方法。有关helper请看<a target="_blank" rel="noopener" href="http://blog.ddlisting.com/2016/03/23/ember-js-ru-men-zhi-nan-zhi-shi-ba-gong-ju-lei-de-zhu-shou/">Ember.js 入门指南之十八工具类的助手</a>。</p>
<h3 id="2，空数组处理"><a href="#2，空数组处理" class="headerlink" title="2，空数组处理"></a>2，空数组处理</h3><p>在each标签内还可以使用<code>{{else}}</code>，当数组为空的时候就会执行else代码块。</p>
<figure class="highlight html"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">&#123;&#123;! 空数组处理，如果从route返回的model为空，则会执行else代码块的代码 &#125;&#125;</span><br><span class="line">&#123;&#123;#each model as |item|&#125;&#125;</span><br><span class="line">    Hello, &#123;&#123;item.name&#125;&#125;</span><br><span class="line">&#123;&#123;else&#125;&#125;</span><br><span class="line">    Sorry, nobody is here.</span><br><span class="line">&#123;&#123;/each&#125;&#125;</span><br></pre></td></tr></table></figure>
<p>为了测试效果，请把<code>app/routes/handlebars.js</code>的<code>return</code>语句改成<code>return []</code>。此时返回到模板上的是一个空数组，结果也和预期的一致，页面显示的是“Sorry, nobody is here.”。</p>
<p>上述的内容就是<code>handlebars</code>的<code>each</code>遍历使用实例。应该也是没什么难度的⋯⋯<br><br></p>
<p>最后感谢的<a target="_blank" rel="noopener" href="http://t.qq.com/falaoyunfeiluan">@吧台丶香槟</a>建议。<br><br><br>博文完整代码放在<a target="_blank" rel="noopener" href="https://github.com/ubuntuvim/my_emberjs_code">Github</a>（博文经过多次修改，博文上的代码与github代码可能又出入，不过影响不大！），如果你觉得博文对你有点用，请在github项目上给我点个<code>star</code>吧。您的肯定对我来说是最大的动力！！</p>

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